1 files changed, 102 insertions, 0 deletions
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/planner/TexturePool.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/planner/TexturePool.h
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+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/planner/TexturePool.h
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+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <compositionengine/Output.h>
+#include <compositionengine/ProjectionSpace.h>
+#include <compositionengine/impl/planner/LayerState.h>
+#include <renderengine/RenderEngine.h>
+
+#include <renderengine/ExternalTexture.h>
+#include <chrono>
+#include "android-base/macros.h"
+
+namespace android::compositionengine::impl::planner {
+
+// A pool of textures that only manages textures of a single size.
+// While it is possible to define a texture pool supporting variable-sized textures to save on
+// memory, it is a simpler implementation to only manage screen-sized textures. The texture pool is
+// unbounded - there are a minimum number of textures preallocated. Under heavy system load, new
+// textures may be allocated, but only a maximum number of retained once those textures are no
+// longer necessary.
+class TexturePool {
+public:
+    // RAII class helping with managing textures from the texture pool
+    // Textures once they're no longer used should be returned to the pool instead of outright
+    // deleted.
+    class AutoTexture {
+    public:
+        AutoTexture(TexturePool& texturePool,
+                    std::shared_ptr<renderengine::ExternalTexture> texture, const sp<Fence>& fence)
+              : mTexturePool(texturePool), mTexture(texture), mFence(fence) {}
+
+        ~AutoTexture() { mTexturePool.returnTexture(std::move(mTexture), mFence); }
+
+        sp<Fence> getReadyFence() { return mFence; }
+
+        void setReadyFence(const sp<Fence>& fence) { mFence = fence; }
+
+        // Disable copying and assigning
+        AutoTexture(const AutoTexture&) = delete;
+        AutoTexture& operator=(const AutoTexture&) = delete;
+
+        // Gets a pointer to the underlying external texture
+        const std::shared_ptr<renderengine::ExternalTexture>& get() const { return mTexture; }
+
+    private:
+        TexturePool& mTexturePool;
+        std::shared_ptr<renderengine::ExternalTexture> mTexture;
+        sp<Fence> mFence;
+    };
+
+    TexturePool(renderengine::RenderEngine& renderEngine) : mRenderEngine(renderEngine) {}
+
+    virtual ~TexturePool() = default;
+
+    // Sets the display size for the texture pool.
+    // This will trigger a reallocation for all remaining textures in the pool.
+    // setDisplaySize must be called for the texture pool to be used.
+    void setDisplaySize(ui::Size size);
+
+    // Borrows a new texture from the pool.
+    // If the pool is currently starved of textures, then a new texture is generated.
+    // When the AutoTexture object is destroyed, the scratch texture is automatically returned
+    // to the pool.
+    std::shared_ptr<AutoTexture> borrowTexture();
+
+protected:
+    // Proteted visibility so that they can be used for testing
+    const static constexpr size_t kMinPoolSize = 3;
+    const static constexpr size_t kMaxPoolSize = 4;
+
+    struct Entry {
+        std::shared_ptr<renderengine::ExternalTexture> texture;
+        sp<Fence> fence;
+    };
+
+    std::deque<Entry> mPool;
+
+private:
+    std::shared_ptr<renderengine::ExternalTexture> genTexture();
+    // Returns a previously borrowed texture to the pool.
+    void returnTexture(std::shared_ptr<renderengine::ExternalTexture>&& texture,
+                       const sp<Fence>& fence);
+    renderengine::RenderEngine& mRenderEngine;
+    ui::Size mSize;
+};
+
+} // namespace android::compositionengine::impl::planner